I am developing a model to estimate groundwater recharge. Towards this objective I’m writing a code in the MATLAB language. I have problem in calculating the amount of infiltration from the river bed. This amount should be then imported to the Richards equation to measure the amount of actual recharge. I need a simple approach (or formula) to calculate the amount of infiltration from the river bed to add to my code. I can’t use any of existing models because I need to add this part to my program code.
Yours sincerely
Sme streams are gaining from water table or groundwater, and some streams are loosing to augement groundwater. And there could be periods of gaining, and periods of loosing. In addition, the substrate below streams is not uniform. When I get into my computer, I will upload a publication by Toth. It may give you some ideas. If the stream leval is higher than the groundwater well level, flow will go toward groundwater. If well level is higher than stream level, water flows to stream (Darcys Law). The substrate supplies the resistence to flow and is measured in hydraulic conductivity. If you know the substrate(s), sometimes this can be estimated, but best to measure, and it is not always uniform in a channel system, and complex. Usually to estimate deep seepage, a water balance is used such as Rainfall = Streamflow +.Evapotranspiration + Change in soil moisture + Deep Seepage. You measure what you can, estimate the others, and deep seepage is what is left over to bslance. Geologic fractures can sometimes remove streamflow and send into deep groundwater storage or movement.
It may be possible to estimate for specific circumstances, but you need to collect some data, unless the stream is down to tight bedrock. A hydrogeologist may know some specifics about your area of interest.
ِDear Dr. William F. Hansen
Thank you for your kind attention and valuable comments.
Dear Dr. Malekian
Thanks for your attention. The problem is that we have just one gauge in the beginning of the stream (upstream) and we have not any gauge in the downstream.
You may not have enough data to accurately estimate gains or losses, multiple streamgages are what is really needed as indicated above. However you may be able to determine if there are gaining stream reaches using temperature differences along the stream.
Please refer to the USGS publication (Professional Paper 1703:pubs.usgs.gov/pp/pp1703/), which provides info on recharge mechanisms in the Arid and Semiarid Southwestern United States.
Valid. Please have a look at this if it would be helpful:
Article Groundwater resources assessment of the Koyna River Basin, India
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